The research that we are carrying out is concerned with the several possible ways in which metalloporphyrins (chlorophyll analogs) interact with methyl viologen (Paraquat) and related compounds. In the coming year, we plan to test the hypothesis that the methyl viologen catalyzed demetallation of chlorophyll may be an alternative model for its herbicidal activity. The oxidation of the methyl viologen radical cation by peroxides will be studied in some detail. We paln to finish our studies on the photo-induced reduction of methyl viologen by organic molecules, to obtain a quantum yield for the photo-induced demetallation, and to test directly the presumed interaction beween methyl viologen and chlorophyll.